If I remember correctly, there are already some scenes of Akane and Juvia with CG, but I imagine there will be more, but as they are secondary characters they will take a little longer than Yui, Marin and Violet (who are the main girls).
Maybe Akane will receive more content in a row, because she is a poll she was first as the favorite secondary character of the public, but Juvia was sixth or fifth, so I guess her content will be slower.
But anyway if you are a fan of Juvia you don't need to worry much, remember that she is a fundamental part to achieve Akane's corruption and also supports Yui and Marin's corruption, so soon Juvia will have a little more content and prominence.
Yes, it will be a major update. What is not clear to me is how it will be released, because the next update is divided into two parts, one that came out a few days ago, and the other that will come out in the middle of the month.
I don't know if Inatari is going to wait to release both parts together, or will release the first part and then the second part.